1. Field of the Invention
The invention relates to a recuperative heat exchanger for gas-gas heat exchange at temperatures above about 700.degree. C. In this specification, heat exchange between a gas and a vapour is included within the scope of the term gas-gas heat exchange as well as heat exchange between a gas and a gas. The invention particularly relates to a heat exchanger comprising a refractory lined vessel having a vertically extending steel shell closed at its top and bottom ends by respective ends, wherein the space within the vessel is divided into respective top and bottom end chambers and a heat-exchange chamber therebetween by top and bottom apertured refractory plates and the end chambers are connected by a plurality of substantially vertical tubes of refractory ceramic material extending between said plates.
2. Description of the Prior Art
Heat exchangers for gas-gas heat exchange at very high temperatures are known from for example blast-furnace technology. There, heat exchangers of the regenerative type are used, in which the heat derived from exhaust gases is stored in ceramic material and combustion air for the blast furnace process is subsequently pre-heated by passing it through this ceramic material. Such exchangers, which are called hot-blast stoves or "cowpers", involve very high investment costs for which reason there have been frequent searches for a gas-gas heat exchanger which is not of the regenerative type but which can be operated as a recuperative heat exchanger at temperatures above 700.degree. C. At temperatures of the order of 700.degree. to 1250.degree. C., metals are not suitable as a construction material for heat exchangers, so that in this temperature range recourse has always been made to regenerative heat exchangers of ceramic material.
GB-A-No. 1100036 describes a heat exchanger as set out in the initial paragraph above. This recuperative heat exchanger has a large number of upright ceramic tubes through which hot combustion gases are passed downwardly so as to heat pressurized air passed upwardly between the tubes. Each tube is in a number of interconnected sections. The tubes are mounted in top and bottom plates within a vessel having domed ends. The upper ends of the tubes are sealed to the top plate but can move through the top plate to allow differential thermal expansion upon heating up and cooling.